which one is correct? - Omitting it does harm the meaning of the sentence?

[Jctgf]

Omitting it does harm the meaning of the sentence?

Does omitting it harm the meaning of the sentence?

Does omit it harm the meaning of the sentence?

Does omit it harms the meaning of the sentence?

Which is the correct one, please?
Thanks.

[Haihao]

Only #2, I think, is correct.

[Jctgf]

hi Haihao,
do you think #1 is possible in a informal talk?
thanks.

[Haihao]

Yes, ictgf. It's not only possible but alright for conversation. BTW, an informal talk is better. :)

[Jctgf]

sorry, "an" informal talk...of course. :oops:
by the way, what does BTW mean?:?:
thanks.

[Haihao]

By The Way.

[Nanucbe]

'by the way' BTW